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  • 148 votes cast
Oct
15
comment Does AES have any fixed-points?
But AES is not a random subset of the $2^{128}!$ permutations on 128 bits; for example, it generates only even permutations. How do we know it doesn't select only from the derangements?
Oct
15
asked Does AES have any fixed-points?
Oct
15
comment Now that quantum computers have been out for a while, has RSA been cracked?
"Their claimed speedup over classical algorithms appears to be based on a misunderstanding of a paper my colleagues van Dam, Mosca and I wrote on "The power of adiabatic quantum computing." That speed up unfortunately does not hold in the setting at hand, and therefore D-Wave's "quantum computer" even if it turns out to be a true quantum computer, and even if it can be scaled to thousands of qubits, would likely not be more powerful than a cell phone." -- Umesh Vazirani, UC Berkeley
Oct
15
comment What are the practical differences between 256-bit, 192-bit, and 128-bit AES encryption?
It should also be noted that 128-bit AES has had a lot more scrutiny than 192- and 256-bit AES.
Oct
12
comment Why has the RSA factoring challenge been withdrawn?
Perhaps RSA needed to invest that money into their new SecurID technology! :)
Oct
9
accepted What is the “Random Oracle Model” and why is it controversial?
Oct
9
awarded  Nice Question
Sep
30
accepted Converting a stream cipher into a block cipher
Sep
30
asked What is the “Random Oracle Model” and why is it controversial?
Sep
29
asked How did the Koblitz/Menezes papers affect the cryptography community?
Sep
28
comment For Diffie-Hellman, must g be a generator?
@Thomas: Improved attacks could also kill DH (or require parameter adjustments). I guess I'm trying to advocate that authors of cryptographic content stop saying (for example) "factoring large integers is impossible" and instead say "there is no publicly-known efficient factoring algorithm on conventional computers". Although I suppose it can get tiresome after a while. Nonetheless, I'm very careful to say the latter when teaching.
Sep
28
comment For Diffie-Hellman, must g be a generator?
Implied in all of the above is "according to current cryptanalysis". The parameters above are a function of (1) our current computing model and (2) our current state of knowledge.
Sep
27
answered Is Diffie-Hellman mathematically the same as RSA?
Sep
27
comment Is modern encryption needlessly complicated?
@Ivo: DES was regarded as "broken" upon release (due to key length); 3DES is still secure (but painfully slow); if you know an attack, please post it. 3DES has an effective key length of at least 110 bits. When I said that DES has never been broken, I mean the construction, not the parameter set.
Sep
27
awarded  Self-Learner
Sep
27
comment In RSA, do I calculate d from e or e from d?
In general, I would trust this site for crypto more than wikipedia since things are vetted here pretty much immediately after they're written.
Sep
27
comment How to fairly select a random number for a game without trusting a third party?
Another fix is to require the number of random bits be higher than (say) 256, and disallow repeated digests. Or better, to force the 2nd publisher of a repeated digest to reveal first (better because it allows you conclusively identify cheaters).
Sep
22
comment Accelerating SHA-1
@fgrieu: Is there a way to see if I'm having cache misses and how much they're costing me?
Sep
22
comment Accelerating SHA-1
@Thomas: reducing my buffer results in no difference in runtime; I'm not sure why you think L1 cache matters here since we process data exactly once (I'm running SHA1 over an 8GiB file).
Sep
22
accepted Accelerating SHA-1